Re: DS9 vs TNG
http://www.treknation.com/articles/ratings_history.shtml
Deep Space Nine spent most of its lifetime as the number one syndicated first-run show on television despite its falling number of viewers. Even when it became a near-serial show (usually, long-term serial shows are ratings disasters -- witness Babylon 5) airing in prime-time in less than 60 percent of the nation, DS9 managed well over a 4.0 average in its final two years. As a general rule, a syndicated show needs to maintain a 3.0 to be successful, DS9 always maintained that despite the strikes against it. Look at the other sci-fi shows similar to DS9: Earth: Final Conflict is regarded as a decent show ratings-wise, staying in the lower 3.0 range and Babylon 5 is the hot potato of science fiction television -- it's done so poorly that no one wants to hold on to it.
As a serial, more cultish television show, DS9 is right behind the X-Files on the all-time list of successes even with extreme disadvantages
http://www.treknation.com/articles/ratings_history.shtml